Abstract:Objective The aim of the study is to evaluate the safety of an endophytic strain Bacillus velezensis (B. velezensis） BR-1 isolated from rice.Method The Comprehensive Antibiotic Resistance Database (CARD) and the Virulence Factor Database (VFDB) were employed to annotate the antibiotic resistance genes and virulence genes, respectively, of BR-1 based on the whole genome sequence. The antibiotic sensitivity test and hemolysis test of BR-1 were performed, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) was used to annotate the genes related to probiotic properties of B. velezensis BR-1.Result The total genome length of B. velezensis BR-1 was 1 071 550 432 bp, with an average GC ratio of 46.3%, containing 4 027 protein-coding genes and 14 CRISPR-Cas. It did not contain genes encoding toxins such as hemolysin BL (Hbl), non-hemolytic enterotoxin (Nhe), enterotoxin (cytotoxin K), and deoxynivalenol (cereulide-Ces). The KEGG annotation revealed genes with good gastrointestinal tolerance, antioxidant activity, and excellent probiotic properties such as acid tolerance, high temperature tolerance, and bile salt tolerance. It was predicted that strain BR-1 contained two antibiotic resistance genes vmlR and clbA. This strain was highly sensitive to 9 antibiotics and did not contain drug-resistant plasmids.Conclusion B. velezensis BR-1 does not contain genes encoding toxins or have broad-spectrum antibiotic resistance and hemolytic activity. It carries genes related to probiotic properties, which meets the safety requirements specified in the General Criteria for Quality and Safety Evaluation of Microbial Fertilizer (GB/T 41728—2022), and can be safely applied as microbial fertilizer.
